I really don't folllow the other stuff that you are saying. During the dwell time, there is a forward and an upward force on the ball. And the more the normal force, the more forward force will be imparted.

If racquet velocity has normal component only (normal to string bed) and point of contact is sweet spot, you hit pure flat FH (forget about strings actions). Because of the absolute symmetry of the ball there always should be solid contact.
If racquet speed has tangential component only, there never will be solid contact.

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Anatoly Antipin - one of the most delicate tennis players in the world.